weeijk

I would ask the Bonsaihunk, Jerry Meislik. He wrote a book about Ficus. http://www.bonsaihunk.us/

Furthermore I have to agree with jbhayman, deepen the wound as deep as you can, so the new callus can overgrow it much easier. I have Ficus Benjaminas with much larger wounds 9x9 inch (4x4 cm). I usually use knobcutters to get deeper in, but with a powertool carver, you can carve the wound deeper out as well, though you have to have steady hands.

Hope this helps, Wessel

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Every tree can be a bonsai, but only some will be.